RMS, which means Root Mean Square, is often (wrongly!!!) used to indicate the continuous power. With a bass guitar, you'll never put a continuous signal on a speaker, so this is quite useless. More useful is the peak rating or program power, which determines the maximum power for short periods of time, like plucking a string. You can use this number to determine the amp power you'll need to get the most out of the speaker, power-wise.

If you use a lot of distortion, very heavy compression, or bass-synthesizer, like the Boss SYB-3, you'll be better off taking the RMS (=contiuous) value as a maximum.

But I gotta admit, I have serious doubts with some major brands' specs too. A 12" car sub that handles 1000W continuous is just ludicrous! That aint no speaker, thats an air heater!

I agree there are discrepancies, but I would actually trust Ampeg's web site sooner than their catalog. The numbers on the site are more sensible than those in the catalog, but I can't be sure of either.

Joris's points about types of signal vs. power rating are good ones. This is stuff that could have been handled via the FAQ that I was hoping would be set up. But regular members can't set it up as a permanent thread or button, so... the same basic questions get asked and answered in perpetuity. (No reflection on Joris, who has contributed a lot of good info on amp topics in various threads.)

The most important thing isn´t the power handling. If the Amp have about 300 W RMS. You don´t need anymore. Just spread the sound through the PA. Too much sound from the same place isn`t god spread it out. Does anyone agree?

Sorry. Me neither. There are lots of situations where one might need 1000W or more on stage. What's with this you-only-need-300W-thing (this is not personal, bas_anton). In a lot of situations, 300W will suffice. A jazz combo player could be perfectly happy with 50W. A demanding heavy metal player could need a 1000. Simply to just be heard over two guitar stacks and a 250 lbs. drummer with a double bass, a china cymbal and drumsticks like trees.

The problem with the numbers is that they have to be interpreted correctly. Music is transitory by nature so continuous power is, in some ways, not the best description anyway. However, we all need a yardstick and the RMS rating of an amp lets us have some measure of comparison because it effectively misses out the element of time that other methods must use for the numbers to be meaningful. And even if the power per unit time were specified would it be meaningful to y' average bass player? I doubt it.

Music power and similar methods of specifying the output power of an amp generate (sometimes very) large numbers which non techies naturally find impressive. 1000 Watts PMP always looks betther than 50 Watts RMS, or whatever.

Even if nobody but techies understands exactly what RMS means, most people accept it as their yardstick.

I say stick to RMS rating.

And, just for the record, I've really no idea whether 300 Watts RMS is loud enough or not.

The numbers on the sight aren't correct anyway. The site says 200/400 watts, but the actual cab is 400/800 watts. The printed catalog is correct. I own the cab and it's printed on the back plate if nobody believes me.

If what you say about the numbers on Ampeg's web site is true, Ampeg has a problem for sure. I believe that *some* of the numbers in the catalog (a few years old) are incorrect, and the web site has better figures (e.g., for some freq. response and sensitivity figures). But if others on the site are also wrong... yuck! It would be nice if they'd get their act together!
- Mike

RMS is basically the average power rating. an amp or speaker should be able to drive the RMS power rating continuously. Peak power, or program power, is the max it can handle in short bursts. Therefore, when choosing an amp and speaker, you should get an amp who's max power matches the speaker's peak power. That way, you can reach that peak power when you need it, but usually it should be running at the RMS rating.